A wireless local area network (WLAN) deployed in a business or enterprise environment comprises numerous access point (AP) devices, each of which is positioned in or near a building to serve wireless client devices. Wireless communication by devices in the WLAN is made in one or more frequency bands: in the case of unlicensed frequency bands, the two common frequency bands in the United States are the 2.4 GHz and the 5 GHz spectrum bands. Some AP devices designed for enterprise deployment can simultaneously operate in both the 2.4 GHz and 5 GHz frequency bands. Such AP devices have two radio transceivers and are referred to as “dual-band AP devices”, indicating that they have a 2.4 GHz radio transceiver and a 5 GHz radio transceiver. When deploying numerous AP devices in a WLAN, it is necessary to assign each AP radio to a certain channel for operation in the corresponding frequency band of operation.
Dynamic Channel Assignment (DCA) schemes have been developed to determine an optimal or close to optimal channel assignment for all AP devices in a given group of AP devices, called a radio frequency (RF) group, in a WLAN deployment. An assignment of channels to all AP devices in an RF group is called a channel plan. DCA schemes can be based on graph coloring techniques, channel plan search/optimization techniques, or a combination of the two.
There are several problems with current search-based DCA schemes. One problem is referred to herein as “pinning” and involves an AP device that happens to be in a “bad spot” insofar as the RF environment is concerned, preventing other AP devices from making channel changes that may otherwise improve their performance in the WLAN. In other words, “the weakest link” AP device in an RF group prevents other AP devices from exploring better channel assignment options.
Cascading is another problem in existing DCA schemes. Cascading is the phenomenon of a channel change for an AP device causing a domino effect where too many other AP devices also change their channel, thereby resulting in network instability and degraded service availability to client devices. Pinning and cascading can be viewed as inter-related problems in the system.
One cause of both cascading and pinning in DCA schemes, in some implementations, is the way that the search for a new channel plan is performed and, in particular, the fact that any potential channel plan changes are controlled by the RF circumstances of a single AP device. A new approach to DCA is needed that ensures multiple, different AP devices can initiate local channel plan changes during any single iteration of channel plan search.